Features, Buffers
*Conan The Librarian (sorry for the slow response - running on an old VAX)
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Library /sys$common/syshlp/lse$clihelp.hlb Features, Buffers *Conan The Librarian (sorry for the slow response - running on an old VAX) |
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A buffer is a temporary holding area that provides a work space for
editing text. You can create a new file or edit an existing file in
a buffer. A buffer becomes visible when it is associated with a
window that is mapped to the screen. Buffers exist only for the
duration of your editing session. When you exit from LSE, the
current buffer is discarded and the contents of the buffer are stored
in a file.
LSE allows you to create multiple buffers. Thus, you can edit
several different files in one editing session. You can create
additional buffers to store portions of text that you might want to
look at, but not edit, during your editing session.
BUFFER ATTRIBUTES
Buffers have many attributes. This section provides details on
buffer attributes and properties. You can use the SHOW BUFFER
command to display the characteristics of one or more buffers.
Buffer Names
A buffer has a name that is displayed in the status line. Buffers
are usually named by the name and type of their associated input
file. The GOTO FILE or GOTO BUFFER commands can create buffers.
Insert/Overstrike
LSE has two text entry modes: insert and overstrike. In insert
mode, text gets inserted into the buffer at the cursor position.
Text to the right of the cursor gets moved. In overstrike mode,
text typed at the cursor replaces text that is currently under the
cursor. When you start an editing session, the buffer is
automatically placed in insert mode. To change the text entry
modes, you use the CHANGE TEXT_ENTRY_MODE command.
Forward/Reverse
LSE maintains a current direction for each buffer. The current
direction is displayed in the status line. This direction is used
for SEARCH operations and the GOTO and ERASE commands. When you
start an editing session, the buffer direction is set to forward.
To set the current direction to forward, you use the SET FORWARD
command. To set the current direction to reverse, you use the SET
REVERSE command. Alternatively, you can use the CHANGE DIRECTION
command to change the current direction.
Input/Output
Buffers may have an associated input or output file. An input file
is a file that is read into a buffer when a buffer is created. An
output file indicates where LSE will write a buffer. This is
usually a new version of an input file. You can change the output
file name with the SET OUTPUT_FILE command. The GOTO FILE command
creates a buffer and reads a file into it.
Read/Write
Buffers have either the read-only or write attribute. The
read-only attribute indicates that the contents of the buffer will
not be written to a file on exit. The write attribute indicates
that the buffer will be written to a file on exit. Usually, a file
is associated with a buffer by the GOTO FILE command, which creates
a buffer and fills it with the contents of a file. When the buffer
is written, it is written to a new version of the file. If no file
is associated with a buffer that has the write attribute, LSE
prompts for a file specification on exit. Note that a buffer is
written only if its contents have been modified.
Modifiable/Unmodifiable
Buffers are either modifiable or unmodifiable. Unmodifiable
buffers protect the contents of a given buffer. You cannot change
an unmodifiable buffer. The GOTO FILE/READ_ONLY and GOTO
SOURCE/READ_ONLY commands create unmodifiable buffers. If you want
to modify an unmodifiable buffer, you must issue the SET MODIFY or
SET WRITE command.
There are some relationships between the READ-ONLY/WRITE buffer
attributes and the UNMODIFIABLE/MODIFIABLE buffer attributes.
Given these attributes, a buffer may be in one of four possible
states. The following list describes these states and explains how
to create these states for a buffer.
o MODIFIABLE - WRITE
The GOTO FILE/WRITE, GOTO SOURCE/WRITE, SET WRITE, and RESERVE
commands set buffers to this state. It is also the default for
the file specified in the LSEDIT command line. The buffer may
be modified and will be written on exit if it has been
modified.
o MODIFIABLE - READ-ONLY
This is the default for the GOTO BUFFER/CREATE command that is
used to create a "scratch" buffer. The buffer may be modified,
but it will not be written on exit.
o UNMODIFIABLE - READ-ONLY
The GOTO FILE/READ_ONLY and GOTO SOURCE/READ_ONLY commands
create buffers in this state. The buffer cannot be modified.
If you issue a SET MODIFY command on this buffer and modify the
contents, LSE will not write the contents on exit unless you
also issue the SET WRITE command for the buffer.
o UNMODIFIABLE - WRITE
A buffer can be set to this state by a user who has completed a
set of changes to a buffer in the MODIFIABLE - WRITE state and
then issued a SET NOMODIFY command for the buffer to protect
the buffer from accidental change for the remainder of the
editing session. LSE will write the file on exit if it has
been changed during the editing session.
System Buffers
Some buffers are used by LSE for special purposes. These are
called system buffers. Unlike user buffers, system buffers do not
correspond to files. You can edit a system buffer like any other
buffer, but you should avoid changing its contents. By convention,
system buffer names start with a dollar sign ($). The most
frequently used system buffers are $HELP, $MESSAGES, $REVIEW, and
$SHOW. System buffers are not displayed by the SHOW BUFFER command
unless you use the /SYSTEM_BUFFERS qualifier.
Languages
Buffers may have a language associated with them. This determines
which language is used for the language-sensitive features. The
file type of your current buffer determines the language LSE uses.
Thus, you can move between different languages in different
buffers, and LSE will provide the interfaces to the appropriate
compilers. The SET LANGUAGE command associates a language with a
buffer.
Current Indentation and Tab Settings
LSE maintains two settings to control the action of the tab key:
current indentation level and tab increment. When you are at the
left margin, the tab key indents to the current indentation level.
If you are not at the left margin, the tab key takes you to the
next tab column based on the tab increment setting. The SET
INDENTATION command sets the current indentation level; the SET
TAB_INCREMENT command sets the size of the tab increment.
Key Bindings
Buffer commands, along with default key bindings are listed under
subtopic "Buffer_Commands".
Additional Information (explode) :
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